Potentiometer



United States Patent Q POTENTIOMETER Etienne de Faymoreau, Nutley, NJ., assignor to International Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Maryland Application November 7, 1955, Serial No. 545,320

12 Claims. (Cl. 2138-148) This invention relates to potentiometers and, more particularly, to the multi-turn type.

In the multi-turn type of potentiometer heretofore known, the contact is moved along the multi-tum resistor turn by turn from one end of the resistor to the other. To return the contact to the starting end of the resistor, the contact must be caused to retrace the multiple turns of the resistor. This is time-consuming for the operator. It is also undesirable in certain systems as DME (distances measuring equipment). In DME the hunting in a reply signal is controlled by the potentiometer, and this requires an abrupt change from a maximum distance seeking to a minimum distance in order to detect a reply and not an echo in place of a reply.

An object of the present invention is to provide a multiple turnl type of potentiometer in which a second contact is brought into engagement with one end of the resistor as the lirst contact reaches or is removed beyond the opposite end of the resistor.

Another object is to provide a sturdy durable potentiometer in which the movable contact is urged with resilient force into positive engagement with the resistor throughout the length of its travel along the resistor.

One of the features of this invention is the provision of an endless race which contains a plurality of contact units, such as metallic balls. A cylindrical member having a surface of insulating material is provided with a helical groove of plural turns therein, and a resistor is disposed lengthwise in the helical groove. The endless race is provided with one section in the fonn of an opensided channel which is disposed adjacent to and crosswise of the turns of the helical groove. A rail is providedin the open channel portion of the race, and resilient means are provided to urge the rail outwardly of the channel so as to cause the contact ball to engage the helical groove and the resistor contained therein. Asthe cylindrical member is rotated relative to the endless race, the ball in the open channel portion of the race is caused by the helical groove to move along the channel and in moving contact with the resistor. When the ball reaches the end of the channel, it engages the end ball of a series of balls contained in the remaining portion of the race transferring movement through the balls to cause the other end ball to be introduced into the opposite end of the channel. In this Way, as soon as the contact unit is moved beyond the one end of the resistor, another contact unit is introduced into engagement with the opposite end of the resistor.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 s a longitudinal cross-sectional view of the potentiometer showing the endless race for the contact units; and

Fig. 2, is a cross-sectional view taken along line 2 2 of Fig. 1.

Referring to the figures of the drawing, the potentilCC ometer is shown to comprise a cylindrical member 1 which may be entirely of insulating material or at least have an inner surface thereof of insulating material. As shown, the cylindrical member 1 is provided with a heli'- cal groove 2 of plural turns from one end to the other of the member 1. Contained in the groove 2 is a resistor 3 preferably of the Kohlrausch coiled type. The resistor is preferably partially imbedded in the insulating material of the cylinder 1, but may be secured thereto by other means if so desired. Each end of the resistor 3 is secured to a slip ring as shown at 4 and 5. The supporting structure for the cylinder 1 comprises two end pieces 6 and 7 and a central cylindrical core 8.

Each of these end pieces, as well as the core, is made up in two parts as best indicated in Fig. 2, the parts 6a and 8a shown in Fig. 2 having been removed in the sectional view of Fig. 1.

An endless ball race 9 is provided in the supporting structure, the ball race extending from one end piece through the core to the other and back again. The core is of cylindrical shape and is disposed axially of the cylindrical member 1 which is rotatably mounted thereon. The core is provided with two sections of the ball race, namely: an interior section 10 and an open-sided section 11. The open-sided section comprises a channel, the open-sided portion of which is disposed adjacent and crosswise of the turns of the helical groove 2. Within the channel is a rail 12 the ends of which extend into the end pieces 6 and 7 which are provided with slots 13 and 14 to limitpthe radial movement of the rail. At spaced points along the rail are two springs 15 and 16 which urge the rail radially outwardly of the channel 11. When a contact ball, such as indicated at 17, is disposed in the channel 11, the rail 12 urges the ball into the helical groove and into engagement with the resistor 3. Only one contact ball is intended to be in the open-sided channel at a time, the remaining portion of the endless race being filled with addiitonal contact balls as indicated at 1S. The cylinder 1 is provided with a gear 19 which meshes with a driving gear 20.

When it is desirable to change the contact setting of the potentiometer, the cylinder 1 is rotated thereby causing the ball 17 by means of the walls of the groove 2 to be moved along the channel 11 and thereby along the resistor 3. The rail 12 ensures positive contact engagement between the ball and the resistor, the contact circuit being through the ball, the rail and the core to the end pieces 6 and 7. To prevent the end balls from entering the channel 11 prematurely cam-like shoulders 21 and 22 are provided adjacent the ends of the rail 12. These shoulders act as resilient stops for the end balls until the ball 17 has been moved beyond one of the ends of the resistor 3. When this takes place, the ball 17 transmits force through the series of balls 18 causing the opposite end ball to be forced over the resilient stop and into the channel 11. This movement, of course, may be in either direction.

It will be clear to those skilled in the art that many variations may be made in the structural design of the potentiometer without departing from the principles of the invention. By way of example, contact units of shape different from ball contacts shown may be provided, the

only requirement being that such contact units be receivable in the helical groove in contact with the resistor 3. While the ball contact tends to roll like a ball-bearing, it may 'also have a sliding contact as well. If the contact unit is shaped differently, it would probably have a sliding contact. Another example is the provision of the shoulders 21 and 22 on the rail 12. Such shoulders may, of course, be made on the wall portions of the end pieces 6 and 7 if such is desired. Furthermore, the helical groove could be located on the outer surface of the cylinv 3V der and, of course, 'the race in that case would be outside the cylinder. Even where the helical groove is on the inner surface of this cylinder the return section of the raceV could. be outside. thecylinder. It is-to be underhaving a cylindrical surface of insulating material, saidl cylindrical surface having therein a lhelical groove of plural turns, a channel defining means stationary relative said cylindrical member deningra guide channelextending adjacent to and crosswise of said turns, a resistor disp .osed lengthwise in said helical groove and a cont-act unit guided by said channel in engagement with said helical groove and said resistor, and means to rotatesaid cylindrical memberV to cause, by means of saidlhelical groove, saidV contact'unit to move along said channel and in moving contact engagement along said resistor.

2. A potentiometer comprising a cylindricall member having a cylindrical surface of insulating material, said cylindrical surface having a helical groove therein of plural turns, a channel dening means stationary relative said cylindrical member defining a guide channel extend ing adjacent to and crosswise of said turnsf,a resistor disposed lengthwise in said helical groove and a contact unit guided by said channel in engagement Vwith saidhelical groove, said path defining means having an element disposed along said channel to urge said unit with resilient force into contact with said resistor, andmeans-to rotate said cylindrical member to cause said contact unit to move along said channel.

3. A potentiometer comprising a. cylindricalv member having a cylindrical surface of insulating material, said cylindrical surface having a helical groove therein of plural turns, stationary means defining a ball race-extending adjacent to and crosswise-of said turns, a resistor disposed lengthwise in said helical groove and a contact ball guided by said race in engagement with said, groove and the re# sistor and means to rotate saidk cylindrical member to cause said contact ball to move along saidpath and in contact engagement along said resistor.

4. AVA potentiometer` comprising a cylindrical member having a cylindrical surface of insulating material, said cylindrical surface having a helical groove therein ofy plural turns,` stationary means defining a ball race extending adjacent to and crosswise of said turns, a resistor disposed lengthwise in said groove and a contact ball guided by said race in engagement with said groove, said race defining meansr having resilient meansdisposed to urge said contact ball with substantially constant resilient force into engagement with said resistor throughoutgmovement of said contact ball along said race, and means to rotate said cylindrical member to cause said ball contact to move alongsaid race.

5. A potentiometer comprising a cylindrical; member having a cylindrical surface of insulating material,` said cylindrical surface having a helical groove therein or" plural turns, stationary means defining an open sided bali race with the open side thereof extending adjacent to and crosswise ofsaid turns, a resistor disposed lengthwise in said groove, a contact ball guided by said race, a rail disposed in said'race, and means to resiliently urge said rail outwardly of said race to cause said ball to extend into Ysaid groovel and engage. said resistor. l

6. A potentiometer comprising a hollow cylindrical member with at least the inner surface thereof of insulating material, sm'd inner surface being grooved to present a helical groove of .plural turns, a resistor disposedin said groove lengthwise thereof, and endless race for contact units disposed withat least onesection of said'raceV adjacent' to ,and crosswise of the turns of said helical groove, aplurality ofcontact units in saidy race, one of said units being; in said section and: the other. of said units filling` substantially completely the remainder of said race, said one section of said race being adapted to position said one unit into said groove in contact with said resistor,

andmeans to rotate said member to cause, by means of said groove, said one unit to move along said race and said resistor, and when said one unit reaches the end of said section it is caused ytortran'sfer movement from unit to unit causing the-last unit kto be-ntr'oduced into they opposite end of said section as said one unit is moved out-of saidfsec'tion. Y

'7. A potentiometer -coinprising al hollow cylindrical member with at least the inner'surfacetlrereof of insulating material, said inner surface-being grooved to present a helical groove of plural turns, a resistor disposed in said groove lengthwise'thereof, and an endless ball race disposed with at least one section of said race adjacent to and crosswise of the turns of said helical groove, a plurality of contactballsin said. race, .oneofY .saidballs being in said section and the other' of said b allsfilling substantially completely the .remainder of said race, said race, having means to resiliently urge said one ball into said grooveV in contact with said resistor, and means. ,to krotate said member to cause said one ball to move along said resistor, and when said one ball reaches the end of said section it is caused to transfer movement fro-rn ball to ball causing the last ball. to be introduced into .the opposite end of said section assaid one ball is movedout of said section.

8. A potentiometer comprising a hollow cylindrical memberwith at least the'inner surface thereoffof insulating material, said inner surface being grooved ,to present a helical groove of plural turns, a resistor disposed in. said groove lengthwise thereof, Ameans supportingy saidmember for rotation, said supportingmeans having.` an endless ball race disposed :with at least one section of .Said race adjacent to and crosswise of the turns of said..helic al groove,.and a plurality of contact balls insaid. race,.one of said balls beingin said sectionand the otherof said balls filling substantially completelythe remainder of said race, said one section being adapted to support said one ball inengagement with-said groove andn saidY resistor, said one ball being moved bysaid groovealongsaid resistor upon rotation kofsaid member, and when .saidone ball reaches the end ofsaid section it is` caused totransfer movement from ball to ball causing: theV lastfballto be introducedV into the vopposite end of saidsectionas said one ball is moved out of said section.

9. A potentiometer comprising a hollowcylindrical member with at least the, inner surface thereof .of .insulating material, said innersurface beinggroovedtopresent-a helical groove of plural turns.aresistor disposed in said groove lengthwise thereof, means supporting said` I memberforV rotation, said supporting means Yhaving an race, one of said ballsrbeing insaid section and the, other of said balls filling substantially completely the remainder of said race, andV means in saidchannel. to resiliently urgeV said. one ball intofsaid groove Vin contact-'with said resistor, said one ball being moved by said groovealongA saidV channel, andwhen` said one ball `reaches theend1of said channel it is caused to transfer movement from-ball to ball causing the last ball to be introduced `into the; op-

Y posite end -of said Vchannel as said onefball' isfmoved out includes ajshoulder; at eachend-.ot ,said channelltozresilif ently resist movement of a ball therepast to ensure the presence of one ball at a time in said channel.

12. A potentiometer comprising a hollow cylindrical member with at least the inner surface thereof of insulating material, said inner surface being grooved to present a hel-ical groove of many turns, a resistor disposed in said groove lengthwise thereof, slip rings carried by said members with each of said rings connected to an end of said resistor, means supporting said member for rotation including a core member receivable axially of said cylindrical member, said supporting means having an endless ball race wherein said core contains an open channel section of said race adjacent to and crosswise of the turns of said helical groove and a return section internally thereof, a plurality of contact balls in said race, one of said balls being in said open channel section and the other of said lballs filling substantially completely the remainder of said race, a rail disposed in said open channel section, means to resiliently urge said rail in a direction out of said channel to cause said one ball to engage said groove and said resistor, and means to rotate said member to cause said one ball to move along said resistor, and when said one ball reaches the end of said section it is caused to transfer movement from ball to ball causing the last ball to be introduced into the opposite end of said section as said one ball is moved out of said section, said rail having means associated therewith at each end thereof to resiliently hold the end b'all from entering said channel until force yis transmitted thereagainst through the series of balls contained in said return sections.

References Cited in the le of this patent UNITED STATES PATENTS 572,593 Barney Dec. 8, 1896 1,620,638 Faller et al Mar. 15, 1927 1,940,102 Roberton Dec. 19, 1933 2,523,896 Bartolomei Sept. 26, 1950 2,712,584 Pantages `luly 5, 1955 FOREIGN PATENTS 246,189 Great Britain Jan. 28, 1926 643,704 Germany Mar. 25, 1937 

